Telephone answering systems are now commonly in use, and incorporate a magnetic tape recorder/player and related control circuitry adapted for connection to local telephone lines and to the base or cradle unit of a conventional telephone. They are programmed so that if the user does not pick, up his telephone from the cradle within a prescribed number of ringing bursts announcing an incoming call, the control circuitry will automatically place an off-hook condition on the telephone line, whereupon the user's prerecorded announcement will be sent to the caller, requesting him to leave his message. Shortly thereafter the recorder is reverted to record mode to record the incoming message, thereafter shutting itself off automatically after a given period of time.
In addition to recording such incoming messages, the answering machine has the capability to play back the recorded messages later over a loudspeaker on the answering machine. Such machines are also normally provided with volume control which will either mute the loudspeaker completely, or allow it to play at a selected volume. This will allow the user at his option to listen to the incoming message, and if he decides that he wishes to converse with the caller, an override system is provided whereby he can pick up a telephone plugged into the answering machine and proceed to converse with the caller. A related feature, known as "remote pickup" will cause this overriding feature to be initiated by picking up any extension phone attached to the same telephone line. With the user in a remote location, he will hear the ringing signal, but will not be able to "screen" the incoming call to decide whether he wishes to speak to the calling party. He may either pickup the telephone or not pickup the telephone at his discretion. Such answering machines are commonly microprocessor-controlled to accommodate a great variety of mode changes and signals, i.e., incoming dial tone after the caller hangs up, automatic record/playback mode, user message recording mode, off-hook and on-hook interconnection to the telephone lines, and other features and modes.
Cordless telephones, completely unrelated to answering machines, are also quite common, such telephones comprising a base unit connected to local telephone lines and a cordless telephone-type handset which the user can carry around with him. The base unit and the handset each contain one of a pair of matched two-channel f.m. duplex transmitter/receivers establishing the communications link therebetween. The handset has a variety of mode switches adapted for various purposes, in particular to alternatively establish "standby" and "talk" modes. When an incoming call comes into the base unit, it sends a corresponding ringing signal to the handset. If the handset is in "standby" mode at the time, a buzzer in the handset emits ringing signal. The user then switches the handset to "talk" mode, at which time voice communication is then established between the base unit and the handset so that the user may talk to the calling party.
The base unit of such a cordless telephone may be plugged into any extension of a telephone line to which an answering machine of the remote-pickup type is connected, and the user will then receive the incoming ringing signal, and may at his option actuate his remote handset to "talk" mode, thereby establishing communication with the incoming caller. He will still, however, be under the disadvantage that he cannot exercise the previously mentioned call-screening function, since he is remote from the loudspeaker as was the previously mentioned case wherein he picks up a conventional extension telephone in a location distant from the answering machine loudspeaker.
There remains a need for a communication system whereby a remote cordless handset can be used interactively with an answering machine in a single integrated base unit, preferably powered by a single microprocessor, and in particular providing a call screening function of the type described hereinbefore.